The systems and methods described herein relate to a process for fabricating a lithographic printing plate using ink jet technology.
Lithography and offset printing methods have long been combined in a compatible marriage of great convenience for the printing industry for economical, high speed, high quality image duplication in small runs and large. Known art available to the industry for image transfer to a lithographic plate is voluminous but dominated by the photographic process wherein a hydrophilic plate is treated with a photosensitive coating, exposed via a film image and developed to produce a printable, oleophilic image on the plate.
While preparing lithographic plates by photographic image transfer is relatively efficient and efficacious, it is a multi-step, indirect process of constrained flexibility. Typically, a photographically presensitized (PS) plate is prepared from a hydrophilically surface-treated aluminum. A positive or negative film image of an original hard copy is prepared and the PS plate exposed to the film image, developed, washed and made ready for print operations. Any desired changes in the film image must be made by first changing the original hard copy and repeating the photographic process; hence, the constrained flexibility. As sophisticated and useful as it is to prepare plates by photographic image transfer, the need for a lithographic plate fabricating process that obviates the above problems associated with the photographic process has long been recognized. Clearly, it would be highly beneficial to the printing industry to directly produce a quality printable image on a plate without proceeding through a multi-step photographic process. It would also be highly efficacious if a process were developed whereby changes could be made in an original image in some predetermined manner without incurring the need to correct hard copy and repeat the photography, particularly if those changes could be made xe2x80x9con-linexe2x80x9d.
Digital computer-aided design of graphical material or text is well known. Electronically derived images of words or graphics presented on the CRT of a digital computer system can be edited and converted to final hard copy by direct printing with impact printers, laser printers or ink jet printers. This manner of printing or producing hard copy is extremely flexible and useful when print runs of no more than a few thousand are required but the print process is not feasible for large runs measured in the tens or hundreds of thousands of pieces. For large runs, printing by lithographic plate is still the preferred process with such plates prepared by the process of photographic image transfer.
It is known that digitized image information can be used in plate making wherein a film is made to express the image according to the image information digitization and an image is formed on the plate by exposure and development. While this method augments flexibility by permitting editing of a digitized image, the method does not overcome the problems associated with the photographic image transfer method of plate fabrication.
Recently, fabrication of lithographic plates by ink jet techniques has been proposed. One such technique is disclosed in Japanese patent application, Kokai 62-25081. This application describes the use of an ink jet system for applying an oleophilic liquid to form an image on the hydrophilic aluminum surface of a lithographic plate. This approach retains the materials and processing of conventional lithographic printing plates and only uses ink jet printing as an alternative in the photomask through which the conventional plates are exposed. U.S. Pat. No. 5,495,803 describes a solid or phase change type of ink jet printing to form a photomask for a printing plate. Thus, these approaches simply are variants of the above platemaking process and do not utilize the ink jet ink image as the hydrophobic image of the plate.
U.S. Pat. No. 4,833,486 discloses the use of an ink jet head to deposit a hot wax upon the surface of a lithographic plate. The hot wax solidifies upon contact with the plate, thus providing an instantaneous printing pattern. Plates prepared by this method are useful for very limited print runs of a few thousand pieces.
There are several advantages for fabricating printing plates by ink jet printers. One advantage is that such processes are environmentally friendly. The complex and potentially polluting chemical preparations and solvents ordinarily used in masking and stripping away photoresist areas of the plates are not always required with ink jet techniques.
The ink jet technology, however, is in its infancy with respect to commercial lithography. Present ink jet techniques cannot produce large or commercially acceptable offset plates. That is, the plates produced by present ink jet techniques have very low plate runs by commercial lithographic standards. Furthermore, there is no ink jet apparatus or process presently available for fabricating large offset plates having a plurality of pages disposed thereon. Indeed, U.S. Pat. No. 4,833,486 teaches that ink jet materials are inexpensive, and therefore, the printing plate may be used a minimum number of times and then discarded. Moreover, in one embodiment of the ""486 patent, it is indicated that the system is designed for non-commercial plate production, inasmuch as an office processor system is proposed. Office processing systems ordinarily are not capable of providing the large amounts of digital information required to produce large, commercial lithographic plates.
A further drawback of the apparatus disclosed in the ""486 patent is that it makes use of an ink jet medium which may be a wax. Wax is a soft material and will abrade with use under the conditions present for commercial offset printing. Even the so-called hard waxes will not provide the durability required for commercial printing runs of the order of 100,000 cycles. Moreover, waxes do not strongly bond to the printing plate surface, i.e., they prefer to remain on the surface, rather than to actively bond to the substrate.
A liquid ink amenable to ink jet technology that provides a stable, durable image on a lithographic plate would simplify and reduce the costs of applying ink jet technology to lithographic printing techniques.
The systems and methods disclosed herein provide inks, liquid at room temperature, which comprise a chromium complex, such as a Werner complex. These inks give rise to durable, hydrophobic layers where they are applied to lithographic plates.
Thus, in one aspect, the systems and methods described herein relate to an ink formulation including about 5-90 weight percent water, up to about 75 weight percent of alcohol, up to about 90 weight percent of ether, and a chromium complex. The alcohol may include one or more of ethanol, isopropanol, isobutanol, trifluoroethanol, and 2-butanol. The ether may include one or more of glyme, diglyme, dioxane, and tetrahydrofuran. In certain embodiments, the ink formulation also includes 0.5-5 weight percent N-methylpyrrolidine. In certain embodiments, the chromium complex comprises a Werner complex, such as pentahydroxy(tetradecanato)dichromium. In certain embodiments, the ink formulation also includes a colored dye. In certain embodiments, the ink formulation includes at least 5 weight percent of ether.
In another embodiment, the systems and methods relate to an ink formulation including about 30-70 weight percent water, up to about 50 weight percent of alcohol, up to about 55 weight percent of ether, and a chromium complex. The alcohol may include one or more of ethanol, isopropanol, isobutanol, trifluoroethanol, and 2-butanol. The ether may include one or more of glyme, diglyme, dioxane, and tetrahydrofuran. In certain embodiments, the ink formulation also includes 0.5-5 weight percent N-methylpyrrolidine. In certain embodiments, the chromium complex comprises a Werner complex, such as pentahydroxy(tetradecanato)dichromium. In certain embodiments, the ink formulation also includes a colored dye. In certain embodiments, the ink formulation includes at least 5 weight percent of ether.
In yet another embodiment, the systems and methods relate to an ink formulation including about 40-60 weight percent water, about 15-33 weight percent of alcohol, about 12-32 weight percent of ether, and a chromium complex. The alcohol may include one or more of ethanol, isopropanol, isobutanol, trifluoroethanol, and 2-butanol. The ether may include one or more of glyme, diglyme, dioxane, and tetrahydrofuran. In certain embodiments, the ink formulation also includes 0.5-5 weight percent N-methylpyrrolidine. In certain embodiments, the chromium complex comprises a Werner complex, such as pentahydroxy(tetradecanato)dichromium. In certain embodiments, the ink formulation also includes a colored dye. In certain embodiments, the ink formulation includes at least 5 weight percent of ether.
In a further embodiment, the systems and methods relate to an ink formulation including about 40-60 weight percent water, about 15-33 weight percent of alcohol, and a chromium complex. The alcohol may include one or more of ethanol, isopropanol, isobutanol, trifluoroethanol, and 2-butanol. In certain embodiments, the ink formulation also includes 0.5-5 weight percent N-methylpyrrolidine. In certain embodiments, the chromium complex comprises a Werner complex, such as pentahydroxy(tetradecanato)dichromium. In certain embodiments, the ink formulation also includes a colored dye. In certain embodiments, the ink formulation includes at least 5 weight percent of ether.
In another aspect, the systems and methods provide an ink jet cartridge for use in an ink jet printer, wherein the cartridge contains an ink formulation as described above. In another embodiment, the systems and methods provide an ink jet printer loaded with an ink formulation as described above.
In yet another aspect, the systems and methods provide methods for preparing an ink formulation by combining about 5-90 weight percent water, up to about 75 weight percent of alcohol, up to about 90 weight percent of ether, and a chromium complex. In another embodiment, the systems and methods provide methods for preparing an ink formulation by combining about 40-60 weight percent water, about 15-33 weight percent of alcohol, about 12-32 weight percent of ether, and a chromium complex. In another embodiment, the systems and methods provide methods for preparing an ink formulation by combining about 40-60 weight percent water, about 15-33 weight percent of alcohol, and a chromium complex. In another embodiment, the systems and methods provide methods for preparing an ink formulation by combining about 30-70 weight percent water, up to about 50 weight percent of alcohol, up to about 55 weight percent of ether, and a chromium complex. The alcohol may include one or more of ethanol, isopropanol, isobutanol, trifluoroethanol, and 2-butanol. The ether may include one or more of glyme, diglyme, dioxane, and tetrahydrofuran. In certain embodiments, 0.5-5 weight percent N-methylpyrrolidine may be added to any of the above mixtures. In certain embodiments, the chromium complex comprises a Werner complex, such as pentahydroxy(tetradecanato)dichromium. In certain embodiments, colored dye may be added to any of the above mixtures. In certain embodiments, at least 5 weight percent of ether is combined with the other components as set forth above.
In a further embodiment, the systems and methods described herein relate to a method of preparing lithographic plates by providing a lithographic plate and disposing an image on the lithographic plate with an ink as described above. In certain embodiments, providing a lithographic plate includes providing a lithographic plate having a hydrophilic layer disposed thereon. In certain embodiments, an ink jet printer is used to dispose the image on the lithographic plate.
In one aspect, the systems and methods described herein relate to an ink formulation including about 50.5 weight percent water, about 23.5 weight percent of alcohol, about 21.7 weight percent of ether, and a chromium complex. In certain embodiments, the chromium complex comprises a Werner complex, such as pentahydroxy(tetradecanato)dichromium. In certain embodiments, the ink formulation also includes a colored dye.
In another aspect, the systems and methods provide an ink jet cartridge for use in an ink jet printer, wherein the cartridge contains an ink formulation as described above. In another embodiment, the systems and methods provide an ink jet printer loaded with an ink formulation as described above.
In yet another aspect, the systems and methods provide methods for preparing an ink formulation by combining about 50.5 weight percent water, about 23.5 weight percent of alcohol, about 21.7 weight percent of ether, and a chromium complex.
The description below pertains to several possible embodiments of the invention. It is understood that many variations of the systems and methods described herein may be envisioned by one skilled in the art, and such variations and improvements are intended to fall within the scope of the invention. Accordingly, the invention is not to be limited in any way by the following disclosure of certain illustrative embodiments.
The systems and methods described herein utilize the properties of chromium complexes to form stable, hydrophobic images on lithographic plates. Suitable complexes include the QUILON complexes, Werner complexes of trivalent chromium and carboxylic acids, e.g., myristic or stearic acid, in isopropyl alcohol (Quilon Chrome Complexes, Dupont Corporation, April, 1992). Such complexes, though available in substantially monomeric, liquid solutions, can be dried and/or cured to provide a polymeric, hydrophobic, water-resistant layer on a wide variety of materials. Furthermore, these layers, presumed to be chemically bonded directly to the surface of the treated material, are quite durable, and thus should allow the production of lithographic plates capable of withstanding the stresses of large print runs.
Inks useful in the systems and methods described herein may include visible dyes or colorants, such as dyes used in conventional inks, or may rely entirely on the presence of the chromium complex to provide an image or residue on a lithographic plate. Solutions of chromium complexes may be formulated using aqueous or non-aqueous solvent mixtures. Solvents which may be employed include protic solvents such as water, methanol, ethanol, trifluoroethanol, n-propanol, iso-propanol, n-butanol, 2-butanol, iso-butanol, t-butanol, n-pentanol, and other protic solvents. Aprotic solvents may be employed, either in place of or in addition to protic solvents, such as acetonitrile, acetone, 1,4-dioxane, tetrahydrofuran, N-methylpyrrolidone, dimethylsulfoxide, 1,2-dimethoxyethane, 1,2-diethoxyethane, dimethylformamide, mineral oil, silicon oil, cellusolve solvents, olive oil, and other polar and non-polar aprotic solvents. In certain embodiments, the ink is substantially free of dihydroxylic solvents and glycols, such as ethylene glycol.
Surfaces suitable for receiving inks such as those described above include supports carrying a receiving layer containing at least one hydrophilic material. Suitable hydrophilic materials may be characterized by: receptivity to the ink to provide an image of the desired quality; surfaces bearing suitable moieties for interaction with the chromium complex in the ink to result in a stable, rugged image; and sufficient hydrophilicity and water-fastness for lithographic printing. These characteristics are well understood by those of skill in the art.
Hydrophilic materials which may be employed in the present invention are polyvinyl alcohols and copolymers thereof, cellulose polymers, polyvinyl acetates and copolymers thereof, polyacrylates and copolymers thereof, polymethacrylates and copolymers thereof, polymaleic anhydrides and derivatives and copolymers thereof, polyvinyl acetals and copolymers thereof, polyvinyl pyrrolidones and copolymers thereof, polyamides, or inorganic polymers. In certain embodiments, the hydrophilic material comprises aluminum boehmite, alumina, a silicate, or silica. Such inorganic polymers are typically formed from a sol gel, colloidal particle deposition, or anodization process to provide a gel or network of inorganic polymer.
Supports useful for carrying a hydrophilic layer as described above include paper, plastic or polymer film or sheets, metals such as aluminum, or any other material suitable for use in an ink jet printing system, as is well known in the art.
In certain embodiments, the printed image may need to be treated or cured to fix or polymerize the ink, such as by exposure to heat. Heat treatment may be accomplished by heating the support or hydrophilic material prior to, during, or after the printing process itself. For example, ink may be printed directly onto a heated surface, or the printed image may afterwards be exposed to a heat source.
In certain embodiments, the hydrophilic layer on the support comprises a catalyst to promote reaction of the chromium complex with the hydrophilic layer. Such a catalyst may comprise an alkaline material or a material bearing polar reactive groups, such as hydroxyls (xe2x80x94OH), amines (such as xe2x80x94NH2, and alkylated derivatives thereof), carboxylates (xe2x80x94CO2xe2x88x92), carboxylic acids (xe2x80x94CO2H), sulfhydryls (xe2x80x94SH), and other suitable groups as will be known to those of skill in the art.
An imaged lithographic printing plate may thus be prepared by providing a support carrying a hydrophilic layer, printing an image on the hydrophilic layer with an ink comprising a chromium complex as described above using an ink jet printer. The image may then optionally be treated, e.g., by heat, to fix the image. In certain embodiments, the support may be heated prior to printing.
In certain embodiments, it may be desirable to provide an ink solution or ink precursor comprising a chromium complex, wherein the ink solution or ink precursor is substantially free of water. Certain complexes of chromium are susceptible to hydrolysis, and suffer from shortened shelf-lives when present in an aqueous solution. Thus, in certain embodiments, a substantially water-free solution of a chromium complex may be combined with an aqueous solution prior to or during the printing process. This can be accomplished by loading an ink jet printer with the two separate solutions, or by providing an ink jet ink cartridge having a solution of a chromium complex in an organic solvent (or mixture of organic solvents) and a separate aqueous solution (or pure water) that can be combined, e.g., in the cartridge or in the printer, as required for printing. The organic solution of chromium may comprise an alcohol or ether, or combinations of alcohols and ethers. The aqueous solution may further comprise a water-miscible solvent, such as an alcohol, e.g., isopropanol, or ether, e.g., tetrahydrofuran. Either or both solutions may further comprise a visible dye, as discussed above.
Thus, an ink jet printer configured for chromium complex-based inks may comprise a mixing mechanism for combining the organic solution of chromium and the aqueous solution, and a printing mechanism for depositing the combination of solutions on a substrate. Because the chromium complexes can form deposits in the mixing and/or printing mechanisms, the printer may further comprise a cleaning mechanism for passing a cleaning solution through these mechanisms to remove or prevent formation of such deposits. In certain embodiments, the aqueous solution, optionally comprising an alcohol such as isopropanol, may be employed as the cleaning solution as well.
Thus, for any of the embodiments and examples described herein, the desired composition of ink containing a chromium complex may be provided as a kit by apportioning the components of the desired composition between two containers, one including the chromium complex and the other containing the water, with the remaining components being divided between the containers in any manner that results in homogenous solutions in the containers. The containers may be joined, e.g., in an ink jet cartridge, or may be separate, e.g., as two independent ink jet cartridges. Where the containers are joined, the two containers may be separated by a destructible or removable barrier, such as a valve or a film, to permit a user to combine the two solutions prior to use.